/*
 * @(#)AttributeFactory.java
 *
 * Copyright 2003-2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package org.wso2.balana.attr;

import org.wso2.balana.ParsingException;
import org.wso2.balana.UnknownIdentifierException;

import java.net.URI;

import java.util.HashMap;
import java.util.Set;

import org.w3c.dom.Node;
import org.wso2.balana.XACMLConstants;

/**
 * This is an abstract factory class for creating XACML attribute values. There
 * may be any number of factories available in the system, though there is
 * always one default factory used by the core code.
 * 
 * @since 1.0
 * @author Seth Proctor
 * @author Marco Barreno
 */
public abstract class AttributeFactory {

	// the proxy used to get the default factory
	private static AttributeFactoryProxy defaultFactoryProxy;

	// the map of registered factories
	private static HashMap registeredFactories;

	/**
	 * static intialiazer that sets up the default factory proxy and registers
	 * the standard namespaces
	 */
	static {
		AttributeFactoryProxy proxy = new AttributeFactoryProxy() {
			public AttributeFactory getFactory() {
				return StandardAttributeFactory.getFactory();
			}
		};

		registeredFactories = new HashMap();
		registeredFactories.put(XACMLConstants.XACML_1_0_IDENTIFIER, proxy);
		registeredFactories.put(XACMLConstants.XACML_2_0_IDENTIFIER, proxy);
		registeredFactories.put(XACMLConstants.XACML_3_0_IDENTIFIER, proxy);

		defaultFactoryProxy = proxy;
	};

	/**
	 * Default constructor. Used only by subclasses.
	 */
	protected AttributeFactory() {

	}

	/**
	 * Returns the default factory. Depending on the default factory's
	 * implementation, this may return a singleton instance or new instances
	 * with each invokation.
	 * 
	 * @return the default <code>AttributeFactory</code>
	 */
	public static final AttributeFactory getInstance() {
		return defaultFactoryProxy.getFactory();
	}

	/**
	 * Returns a factory based on the given identifier. You may register as many
	 * factories as you like, and then retrieve them through this interface, but
	 * a factory may only be registered once using a given identifier. By
	 * default, the standard XACML 1.0 and 2.0 identifiers are regsietered to
	 * provide the standard factory.
	 * 
	 * @param identifier
	 *            the identifier for a factory
	 * 
	 * @return an <code>AttributeFactory</code>
	 * 
	 * @throws UnknownIdentifierException
	 *             if the given identifier isn't registered
	 */
	public static final AttributeFactory getInstance(String identifier)
			throws UnknownIdentifierException {
		AttributeFactoryProxy proxy = (AttributeFactoryProxy) (registeredFactories
				.get(identifier));

		if (proxy == null)
			throw new UnknownIdentifierException("Uknown AttributeFactory "
					+ "identifier: " + identifier);

		return proxy.getFactory();
	}

	/**
	 * Sets the default factory. This does not register the factory proxy as an
	 * identifiable factory.
	 * 
	 * @param proxy
	 *            the <code>AttributeFactoryProxy</code> to set as the new
	 *            default factory proxy
	 */
	public static final void setDefaultFactory(AttributeFactoryProxy proxy) {
		defaultFactoryProxy = proxy;
	}

	/**
	 * Registers the given factory proxy with the given identifier. If the
	 * identifier is already used, then this throws an exception. If the
	 * identifier is not already used, then it will always be bound to the given
	 * proxy.
	 * 
	 * @param identifier
	 *            the identifier for the proxy
	 * @param proxy
	 *            the <code>AttributeFactoryProxy</code> to register with the
	 *            given identifier
	 * 
	 * @throws IllegalArgumentException
	 *             if the identifier is already used
	 */
	public static final void registerFactory(String identifier,
			AttributeFactoryProxy proxy) throws IllegalArgumentException {
		synchronized (registeredFactories) {
			if (registeredFactories.containsKey(identifier))
				throw new IllegalArgumentException("Identifier is already "
						+ "registered as " + "AttributeFactory: " + identifier);

			registeredFactories.put(identifier, proxy);
		}
	}

	/**
	 * Adds a proxy to the factory, which in turn will allow new attribute types
	 * to be created using the factory. Typically the proxy is provided as an
	 * anonymous class that simply calls the getInstance methods (or something
	 * similar) of some <code>AttributeValue</code> class.
	 * 
	 * @param id
	 *            the name of the attribute type
	 * @param proxy
	 *            the proxy used to create new attributes of the given type
	 * 
	 * @throws IllegalArgumentException
	 *             if the given id is already in use
	 */
	public abstract void addDatatype(String id, AttributeProxy proxy);

	/**
	 * Returns the datatype identifiers supported by this factory.
	 * 
	 * @return a <code>Set</code> of <code>String</code>s
	 */
	public abstract Set getSupportedDatatypes();

	/**
	 * Creates a value based on the given DOM root node. The type of the
	 * attribute is assumed to be present in the node as an XAML attribute named
	 * <code>DataType</code>, as is the case with the AttributeValueType in the
	 * policy schema. The value is assumed to be the first child of this node.
	 * 
	 * @param root
	 *            the DOM root of an attribute value
	 * 
	 * @return a new <code>AttributeValue</code>
	 * 
	 * @throws UnknownIdentifierException
	 *             if the type in the node isn't known to the factory
	 * @throws ParsingException
	 *             if the node is invalid or can't be parsed by the appropriate
	 *             proxy
	 */
	public abstract AttributeValue createValue(Node root)
			throws UnknownIdentifierException, ParsingException;

	/**
	 * Creates a value based on the given DOM root node and data type.
	 * 
	 * @param root
	 *            the DOM root of an attribute value
	 * @param dataType
	 *            the type of the attribute
	 * 
	 * @return a new <code>AttributeValue</code>
	 * 
	 * @throws UnknownIdentifierException
	 *             if the data type isn't known to the factory
	 * @throws ParsingException
	 *             if the node is invalid or can't be parsed by the appropriate
	 *             proxy
	 */
	public abstract AttributeValue createValue(Node root, URI dataType)
			throws UnknownIdentifierException, ParsingException;

	/**
	 * Creates a value based on the given DOM root node and data type.
	 * 
	 * @param root
	 *            the DOM root of an attribute value
	 * @param type
	 *            the type of the attribute
	 * 
	 * @return a new <code>AttributeValue</code>
	 * 
	 * @throws UnknownIdentifierException
	 *             if the type isn't known to the factory
	 * @throws ParsingException
	 *             if the node is invalid or can't be parsed by the appropriate
	 *             proxy
	 */
	public abstract AttributeValue createValue(Node root, String type)
			throws UnknownIdentifierException, ParsingException;

	/**
	 * Creates a value based on the given data type and text-encoded value. Used
	 * primarily by code that does an XPath query to get an attribute value, and
	 * then needs to turn the resulting value into an Attribute class.
	 * 
	 * @param dataType
	 *            the type of the attribute
	 * @param value
	 *            the text-encoded representation of an attribute's value
	 * @return a new <code>AttributeValue</code>
	 * 
	 * @throws UnknownIdentifierException
	 *             if the data type isn't known to the factory
	 * @throws ParsingException
	 *             if the text is invalid or can't be parsed by the appropriate
	 *             proxy
	 */
	public AttributeValue createValue(URI dataType, String value)
			throws UnknownIdentifierException, ParsingException {
		return createValue(dataType, value, null);
	}

	/**
	 * Creates a value based on the given data type and text-encoded value. Used
	 * primarily by code that does an XPath query to get an attribute value, and
	 * then needs to turn the resulting value into an Attribute class.
	 * 
	 * @param dataType
	 *            the type of the attribute
	 * @param value
	 *            the text-encoded representation of an attribute's value
	 * @param params
	 *            additional parameters that need to creates a value
	 * @return a new <code>AttributeValue</code>
	 * 
	 * @throws UnknownIdentifierException
	 *             if the data type isn't known to the factory
	 * @throws ParsingException
	 *             if the text is invalid or can't be parsed by the appropriate
	 *             proxy
	 */
	public abstract AttributeValue createValue(URI dataType, String value,
			String[] params) throws UnknownIdentifierException,
			ParsingException;

}
